A variety of organic phosphite compounds have been prepared and proposed for use as stabilizers, particularly to protect polymers from the degradative effects of heat and oxygen. Some of these materials have been used with varying degrees of success, and some of them have found use in combination with hydroxyphenylalkyleneyl isocyanurates to enhance the activity of the isocyanurates. Improved, less expensive, phosporous containing compounds that are useful as polymer stabilizers, and particularly those which form useful combinations with the hydroxyphenylalkyleneyl isocyanurates are desired, along with increased resistance to hydrolysis in polymer applications.